useMapClass

PUBLIC:
Configure the mapping to use an instance of the specified container class
to hold the target objects. The key used to index a value in the
Map is the value returned by a call to the specified
zero-argument method.
The method must be implemented by the class (or a superclass) of any
value to be inserted into the Map.

The container class must implement (directly or indirectly) the
java.util.Map interface.

To facilitate resolving the method, the mapping's referenceClass
must set before calling this method.